Silent propeller



E. J. PRUCHA SILENT PROPELLER Filed Oct. 22, 1941 2 Sheets-Sheet 1 .Zi'mil. llrucka, I INVENTOR.

A'ITDRNIYB Nov. 2, 1943.

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SILENT PROPELLER Filed Oct. 22, 19 41 2 Sheets-Sheet 2 Maw/Z1415:

' '42 71:22 Jfiacka,

INVENTOR.

Nov. 2, 1943.

Patented Nov. 2, 1943 l .KTS I LElVT PROPELLER f g n' ohnrmelia, ConventStation- N. J

Application October 22, 1941, Serial No. 416,112 q 7 Claims; (015170 172;

My invention relates to aircraft and has among its objects and advantages the provision of an improved propeller blade designed to eliminate the whirring noises peculiar to the rotating propeller.

In the accompanying drawings:

Figure 1 is a view of a propeller blade in accordance with my invention;

Figure 2 is a view of the trailing edge of the blade;

Figure 3 is a sectional view taken along the line 33 of Figure 1;

Figure 4 is a sectional View taken along the line 44 of Figure 1; and

Figure 5 is an enlarged plan view of a portion of the blade.

In the embodiment selected for illustration, 1

make use of a conventional propeller blade lllenclosed in a covering l2 of sponge rubber. The entire blade I 0 is enclosed in the covering 12, with the exception of the shank 14 adjacent the hub I 6.- Outside the covering I2 is provided a canvas covering 18, which canvas covering completely encloses the sponge rubber covering I2. Enclosing the canvas covering I8 is an outside covering 23 of semi-hard rubber. Rubber covering completely enclosesthe canvas covering Extending longitudinally of the blade I 0 upon both its sides are two rows 22 and 24 of metallic eyelets or grommets 26 in the canvas covering I8. The rows 22 are spaced from theleading edge 28 of the blade Ill equal distances. The rows 24 are also spaced equal distances from the trailing edge 30 and at distances corresponding sheets 36, each provided with two rows of slots 38. Both sheets belly outwardly over the respective rowsof louvers 3'2 and 34 and the longitudinal center areas of the two sheets are rein-.

forced by I beams secured to the rubber covering 20. The marginal edges of the two aluminium sheets 36 are fixedly secured to the rubber covering 20 by rivets 42 extending through the blade In. The rubber covering 20 is depressed throughout the areas engaged by the-margins of the aluminium sheets 36 so as to bring the outer surfaces of the latter flush with the surrounding rubber covering.

The leading and trailingedges' of the rubber covering 20 terminate in wedge formations 42',

each of whichis providedwith closely spaced transverse openings 44, which openings are also provided in the tip margin 46 ofthe. rubber covering- Both the canvas covering l8 and rubber covering 20 are provided with zipper fastenings 48 and 50 extending from the length I4 partially along the trailing'edge 30 of the blade l0. Screws 52 extend through the sponge rubber cov-. ering l2, the canvas covering l8 and the rubber covering 20 at their ends about the shank I 4,

which screws are threaded into the rubber covering and extended into bores 54 in the shank l4. The louvers in therespective rows 32' and 34 are,

slightly spaced end to end, and the rubber covering 20 throughout the areas between the spaced .53

louvers are provided with metallic eyelets which operate to cushion the louvers.

In operation, air trapped in the leading rows of louvers 32 passes through the eyelets26 and between the sponge rubber covering l2 and the canvas 18, the air exhausting through the eyelets 26 associated with the .rows of trailing louvers 34. The I beams 40 engage the rubber-covering 20 to-restrain the covering from bellying in an excessive degree from the covering l2- The bellied formation of the aluminium sheets 36, when viewed according to Figure 4, provides an element of resiliency or cushioning characteristics accommodating a predetermined degree of expansion of the rubber covering, When the blade I0 is stationary, the rubber covering 20 firmly engages the canvas covering l4 and presses the latter against the sponge rubber'covering I2 throughout its entire outer surface. The openings 44 in the wedge formations 42 break down the stiffness of these formations so as to lend cushioning properties thereto. r

Without further elaboration, the foregoingwill so fully illustrate my invention, that others may, by applying current knowledge, readily adapt the same foruse under various'conditions of service. I

I claim:

I 1. The combination of apropeller blade 3, re-

silient covering for the blade, a second covering enclosing the resilient covering and. being provided with a row of air inlet openings extending longitudinally of the'blade on one side thereof and a row of air outlet openings extending longitudinally of the blade rearwardly of said first mentioned row and on the same side of the blade,

and a resilient covering over said second covering and provided with air inlet louvers and air outlet louvers respectively aligned with said air inlet openings and said air outlet openings.

' 2. The invention described in claim 1 wherein all of said coverings are riveted to the blade about its peripheral portion.

3. The invention described in claim 1 wherein said semi-resilient covering includes wedge shaped formations about the peripheral portions of the blade "and in the plane of the blade;

4. The invention described in claim 1 wherein said resilient covering comprises sponge rubber said second covering comprises canvas and said semi-resilient covering comprises rubber. v

' 5. The invention described in claim 1 wherein 1 fastening pins are providediorall the coverin s. j .I' about the shank of the blade, and in which said second covering and said semi-resilient covering are provided with slide fasteners extending partially along the trailing edge of the blade.

6. The invention described in claim 1 wherein said air inletopenings and said air outlet openings and said air inlet louvers and the outlet louvers are provided on both front and rear faces of the blade.

'7. The invention described in claim 1 wherein said air inlet openings and air outlet openings and said air inlet louvers and the outlet louvers are provided on both front and rear faces of the blade, slotted metallic sheets (extending over the air inlet and airoutlet louvers andfixedly secured to the blade, said metallic sheets being bellied outwardly over the respective air inlet and air outlet louvers and engaging 'saidZSe'mi-reSiIient covering along lines between the respective rowstof air inlet and air outlet louvers.

EMIL JOHN PRUCHA. 

